[MLB-WIRELESS] Bullet2 output power, why 1W or 100mW

[mw at freenet.net.au]

G'day,

Yeah, I can't think of many applications that would need a 1Watt
transmitter.  That's not to say that there are no applications for one, just
that I can't think of many ;-)

1Watt is about 30dBm, which means that your maximum antenna size is just
6dBi to keep within the 36dB EIRP limit.

Now, consider a point to point link of about 50Km.  Theoretically you lose
about 135dB signal through the air, so if you start with 26dB at the
transmit end, by the time you go 20Km, you only have -99 to work with.  If
your antenna is a meagre 6dBi, then the best possible result at the receiver
is a measly -93: barely enough to do anything with it.

BUT, if you used a 170mW transmitter, which is about 22dBm, then you can use
a 14dBi antenna.  So over a 50Km link, you could potentially get -85dBm of
signal to the receiver.  That's more likely to produce a reasonably usable
result.

The only reason I can think of that you would want to use a 1W transmitter
would be when you want to do a relatively short hop point to point link
(like less than 5Km perhaps), and you wanted to use small, aesthetically
unobtrusive, antennas.

Cheers!

> -----Original Message-----
> From: melbwireless-bounces at wireless.org.au [mailto:melbwireless-
> bounces at wireless.org.au] On Behalf Of Russell Smith
> Sent: Sunday, 1 March 2009 2:38 PM
> To: 'Melbourne Wireless'
> Subject: [MLB-WIRELESS] Bullet2 output power, why 1W or 100mW
> 
> Hi,
> 
> I am a little confused about the power stuff relating to output power of
> the wireless AP's.  Particularly the Bullet2's.  They come in 1W and
> 100mW.  From what I can tell by calculating EIRP's there is no need to
> even use more than 100mW if you have a directional 18dB+ antenna.  It
> seems that the only reason for 1W is for lower gain Onmi antenna's to
> get more power from them.
> 
> Does anybody have an insight into this area?  I am very much a newbie
> and am not sure what equipment I am best to buy.
> 
> Regards
> 
> Russell Smith
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